Determination of quinoxaline-2-carboxylic acid, the major metabolite of carbadox, in porcine liver by isotope dilution gas chromatography-electron ... [An article from: Analytica Chimica Acta]

This digital document is a journal article from Analytica Chimica Acta, published by Elsevier in 2004. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
A sensitive and robust method using isotope dilution gas chromatography-electron capture negative chemical ionization mass spectrometry (GC-ECNI-MS) was developed and validated for the analysis of quinoxaline-2-carboxylic acid (QCA) in porcine liver. [^2H"4]QCA was added to liver samples which were then deproteinated with 2% metaphosphoric acid in 20% methanol. Followed by sequential extraction with water-saturated ethyl acetate and phosphate buffer, the buffer extracts were subject to solid-phase extraction clean-up by mixed mode anion-exchange columns. QCA was derivatized with N-methyl-N-tert-butyldimethylsilyltrifluoroacetamide (MTBSTFA) prior to GC-ECNI-MS determination. For unambiguous identification, a second GC-ECNI-MS experiment was performed on suspected positive samples which were derivatized independently with another derivatization agent, trimethylsilyldiazomethane. Excellent recovery and precision were obtained and the limit of quantitation was 0.7@mg/kg (S/N>60). Method ruggedness by Taguchi orthogonal array technique is also presented.